1. Field of the Invention
This invention relates to an image reading device and an image reading method that can perform switching between reading of a document on a flatbed transparent member and reading of a document fed from an automatic document feeder device to read the document.
2. Description of the Related Art
For example, Japanese Patent Laid-Open No. 2004-349911 discloses an image reading device in which an FB (Flatbed) image reading device and an ADF (Automatic Document Feeder) device are integrated. Such an image reading device is capable of, after a document is laid on the FB transparent member (Flatbed transparent member), moving a reading unit in the sub scanning direction to read the stopped document. Hereinafter, such reading will be referred to as FB reading (Flatbed reading). Also the image reading device is capable of bringing the reading unit to a standstill to read, through a transparent member, a document fed from the ADF device and then delivering the read document to an exit unit. Hereinafter, such reading will be referred to as ADF reading (Automatic Document Feeder reading), and the transparent member used in the ADF reading will be referred to as an ADF transparent member (Automatic Document Feeder transparent member).
On the other hand, in the image reading device, calibration of the reading unit is performed to cause the reading unit to acquire image data with the fidelity of color tones to the document. Typically, the reading unit is operated to read a color reference sheet to acquire calibration data, and then calibration of the reading unit is performed on a basis of the acquired calibration data. In an image reading device capable of switching between the FB reading and the ADF reading, a common calibration process for the FB reading and the ADF reading is performed in most cases.
However, in the image reading device employing different members for the FB transparent member and the ADF transparent member as disclosed in Japanese Patent Laid-Open No. 2004-349911, the image reading device is incapable of achieving color correction suitable for each of the FB reading and the ADF reading by the common calibration process. For example, it is conceivable that, for the ADF reading, the color reference sheet may be read in a predetermined position and, based on this, calibration of the reading unit may be performed, and then for the FB reading, the result of this calibration may be applied to the reading unit without any change. However, in the case of performing such common calibration, the FB reading by the reading unit may possibly result in improper reading because of a difference in color tones of transmitted light between the FB transparent member and the ADF transparent member. For example, the FB transparent member may be formed of strongly bluish glass and the ADF transparent member may be formed of strongly yellowish resin. Further, even if the FB transparent member and the ADF transparent member are formed of the same material, their color tones may possibly differ from each other due to color-tone variations caused by big volume production and/or aged deterioration of the transparent member. In such a case, even if the same document is read by the FB reading and the ADF reading after the common calibration process has been executed, the read images thus obtained may differ in color tones.